Not really. There have been cases where a particular morph was associated with weakness/problems, but most of those problems go away with some outcrossing. So, yes it can happen, but no, it is not the rule.

It is frustrating when things like this happen, a seemingly healthy robust animal just takes a turn for the worst. Contributing factors can be any of the following:

1. Inherent problem, out of your control2. Problem from too much inbreeding (lots of debates on how much is too much, but still a factor)3. Allergies/reactions of the snakes to the substrate you are using.4. Chemicals in the water (use bottled water for snakes)5. Cage material off-gassing (again, questionable)

You might want to look at your substrate and cages. It could be that a morph with a slightly less effective immune system will have problems in your setup while other snakes can cope. Just some thoughts, not accusing you or anything. And of course, it could be something out of your control completely. Were these animals from the same source or breeder?